U.S. patent number 7,484,548 [Application Number 11/433,107] was granted by the patent office on 2009-02-03 for continuous casting of reactionary metals using a glass covering.
This patent grant is currently assigned to RMI Titanium Company. Invention is credited to Michael P. Jacques, Brian W. Martin, Frank P. Spadafora, Kuang-O Yu.
United States Patent |
7,484,548 |
Jacques , et al. |
February 3, 2009 |
**Please see images for:
( Certificate of Correction ) ** |
Continuous casting of reactionary metals using a glass covering
Abstract
A seal for a continuous casting furnace having a melting chamber
with a mold therein for producing a metal cast includes a passage
between the melting chamber and external atmosphere. As the cast
moves through the passage, the cast outer surface and the passage
inner surface define therebetween a reservoir for containing liquid
glass or other molten material to prevent the external atmosphere
from entering the melting chamber. Particulate material fed into
the reservoir is melted by heat from the cast to form the molten
material. The molten material coats the cast as it moves through
the passage and solidifies to form a coating to protect the hot
cast from reacting with the external atmosphere. Preferably, the
mold has an inner surface with a cross-sectional shape to define a
cross-sectional shape of the cast outer surface whereby these
cross-sectional shapes are substantially the same as a
cross-sectional shape of the passage inner surface.
Inventors: |
Jacques; Michael P. (Canton,
OH), Spadafora; Frank P. (Niles, OH), Yu; Kuang-O
(Highland Heights, OH), Martin; Brian W. (N. Canton,
OH) |
Assignee: |
RMI Titanium Company (Niles,
OH)
|
Family
ID: |
38694430 |
Appl.
No.: |
11/433,107 |
Filed: |
May 12, 2006 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20060254746 A1 |
Nov 16, 2006 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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10989563 |
Nov 16, 2004 |
7322397 |
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Current U.S.
Class: |
164/268;
164/439 |
Current CPC
Class: |
B22D
11/07 (20130101); B22D 11/1213 (20130101) |
Current International
Class: |
B22D
11/10 (20060101) |
Field of
Search: |
;164/439,263,268,472,488,256,513 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Kerns; Kevin P
Attorney, Agent or Firm: Sand & Sebolt
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of U.S. patent
application Ser. No. 10/989,563, filed Nov. 16, 2004, now U.S. Pat.
No. 7,322,397; the disclosure of which is incorporated herein by
reference.
Claims
The invention claimed is:
1. An apparatus comprising: a continuous casting mold adapted for
producing a metal casting having an outer periphery; a molten bath
of a coating material disposed below the mold and adapted for
applying a coating of molten material to an outer periphery of the
metal casting to produce a coated metal casting; a metal casting
pathway extending downwardly from the mold to adjacent the molten
bath and adapted for movement of the metal casting therein from the
mold to the molten bath; and a first temperature sensor for sensing
temperature at a first sensing location on the pathway whereby the
first temperature sensor is adapted to measure the temperature of
the metal casting at the first sensing location.
2. The apparatus of claim 1 further including a first heat source
disposed below the mold, above the molten bath and adjacent the
pathway whereby the first heat source is adapted for selectively
heating the metal casting as it moves along the pathway; and
wherein the first temperature sensor is part of a control system
configured to control operation of the first heat source in
accordance with the temperature sensed at the first sensing
location on the pathway by the first temperature sensor.
3. The apparatus of claim 2 wherein the first heat source includes
an induction coil which circumscribes the pathway.
4. The apparatus of claim 2 wherein the first sensing location is
below the heat source and above the molten bath.
5. The apparatus of claim 4 further including a second heat source
disposed outwardly of and adjacent the molten bath for selectively
heating the molten bath; and a second temperature sensor for
sensing a temperature of the molten bath.
6. The apparatus of claim 5 further including a passage wall having
an inner periphery which defines a passage adapted for the metal
casting to move through; wherein the inner periphery bounds the
molten bath; and wherein the second temperature sensor is
configured to sense a temperature of the passage wall whereby the
second temperature sensor is configured to sense the temperature of
the molten bath.
7. The apparatus of claim 1 further including a source of
particulate material and a dispenser for dispensing the particulate
material to a location adjacent the molten bath.
8. The apparatus of claim 7 further including a cooling device
disposed closely adjacent a portion of the dispenser for cooling
the particulate material therein whereby the cooling device is
adapted to prevent melting of the particulate material within the
dispenser.
9. The apparatus of claim 8 wherein the dispenser includes a
conduit for carrying the particulate material; wherein the conduit
has an exit end disposed adjacent the molten bath; and wherein the
cooling device is disposed closely adjacent the conduit.
10. The apparatus of claim 7 further including a metal casting
pathway extending from adjacent the mold to adjacent the molten
bath and adapted for movement of the metal casting therein from the
mold to the molten bath; wherein the dispenser includes a conduit
for carrying the particulate material; and wherein the conduit has
an exit end disposed adjacent the pathway.
11. The apparatus of claim 7 further including a passage wall
having an inner periphery which defines a passage adapted for the
metal casting to move through; wherein the inner periphery bounds
the molten bath; and wherein the dispenser is configured to
dispense the particulate material to a location within the inner
periphery of the passage wall.
12. The apparatus of claim 1 further including a cutting mechanism
disposed below the molten bath and adapted for cutting the coated
metal casting while extending downwardly from the mold to form cut
segments of the coated metal casting; and a removal mechanism
disposed below the cutting mechanism and adapted for removing the
cut segments of the metal casting from a cutting position at which
the cut segments separate from a parent segment of the coated metal
casting.
13. The apparatus of claim 12 wherein the removal mechanism
includes first and second rotatable removal rollers which are
spaced from one another to define therebetween a cut segment
engaging space and which are adapted to rollably engage and support
one of the cut segments disposed in the space.
14. The apparatus of claim 12 further including a casting-lowering
mechanism disposed above the cutting mechanism and adapted for
lowering the coated metal casting.
15. The apparatus of claim 1 further including a cutting mechanism
disposed below the molten bath and adapted for cutting the coated
metal casting while extending downwardly from the mold to form cut
segments of the coated metal casting; and a casting-lowering
mechanism disposed above the cutting mechanism and adapted for
lowering the coated metal casting.
16. The apparatus of claim 15 wherein the lowering mechanism
includes first and second rotatable lowering rollers which are
spaced from one another to define therebetween a coated metal
casting engaging space and which are adapted to rollably engage and
support the coated metal casting when disposed in the space.
17. The apparatus of claim 1 further including a melting chamber
which has a sidewall and in which the mold is disposed; and a
passage wall having an inner periphery defining a passage which
extends through the sidewall of the melting chamber and is adapted
for movement of the metal casting therethrough; and wherein the
molten bath is bounded by the inner periphery of the passage
wall.
18. The apparatus of claim 17 further including a hearth defining a
molten material containing cavity; and wherein the hearth is
disposed within the melting chamber and adapted for transferring
molten material therefrom into the mold.
19. In combination, a heated metal casting having an outer
periphery and a furnace for producing the metal casting, the
furnace comprising: a continuous casting mold for producing the
heated metal casting; a molten bath of a coating material disposed
below the mold for applying a coating of molten material to the
outer periphery of the metal casting to produce a coated metal
casting; a source of particulate material; a dispenser for
dispensing the particulate material to a location adjacent the
molten bath; a metal casting pathway extending from adjacent the
mold to adjacent the molten bath for transporting the metal casting
therein from the mold to the molten bath; and a first heat source
disposed below the mold, above the molten bath and adjacent the
pathway whereby the first heat source is configured to heat the
metal casting as it moves along the pathway so that the heated
metal casting radiates heat to the particulate material to
facilitate melting the particulate material to form the molten
bath.
20. The apparatus of claim 19 wherein the first heat source
includes an induction coil which circumscribes the pathway.
21. The apparatus of claim 19 further including a cooling device
disposed closely adjacent a portion of the dispenser for cooling
the particulate material therein whereby the cooling device is
adapted to prevent melting of the particulate material within the
dispenser.
22. The apparatus of claim 21 wherein the dispenser includes a
conduit for carrying the particulate material; wherein the conduit
has an exit end disposed adjacent the molten bath; and wherein the
cooling device is disposed closely adjacent the conduit.
23. The apparatus of claim 19 wherein the dispenser includes a
conduit for carrying the particulate material; and wherein the
conduit has an exit end disposed adjacent the pathway.
24. The apparatus of claim 19 further including a passage wall
having an inner periphery which defines a passage adapted for the
metal casting to move through; wherein the inner periphery bounds
the molten bath; and wherein the dispenser is configured to
dispense the particulate material to a location within the inner
periphery of the passage wall.
25. The apparatus of claim 19 further including a melting chamber
which has a sidewall and in which the mold is disposed; and a
passage wall having an inner periphery defining a passage which
extends through the sidewall of the melting chamber and is adapted
for movement of the metal casting therethrough; and wherein the
molten bath is bounded by the inner periphery of the passage
wall.
26. An apparatus comprising: a continuous casting mold adapted for
producing a metal casting having an outer periphery; a molten bath
of a coating material disposed below the mold and adapted for
applying a coating of molten material to the outer periphery of the
metal casting to produce a coated metal casting; and a source of
particulate material and a dispenser for dispensing the particulate
material to a location adjacent the molten bath.
27. The apparatus of claim 20 further including a cooling device
disposed closely adjacent a portion of the dispenser for cooling
the particulate material therein whereby the cooling device is
adapted to prevent melting of the particulate material within the
dispenser.
28. The apparatus of claim 27 wherein the dispenser includes a
conduit for carrying the particulate material; wherein the conduit
has an exit end disposed adjacent the molten bath; and wherein the
cooling device is disposed closely adjacent the conduit.
29. The apparatus of claim 20 further including a metal casting
pathway extending from adjacent the mold to adjacent the molten
bath and adapted for movement of the metal casting therein from the
mold to the molten bath; wherein the dispenser includes a conduit
for carrying the particulate material; and wherein the conduit has
an exit end disposed adjacent the pathway.
30. The apparatus of claim 20 further including a passage wall
having an inner periphery which defines a passage adapted for the
metal casting to move through; wherein the inner periphery bounds
the molten bath; and wherein the dispenser is configured to
dispense the particulate material to a location within the inner
periphery of the passage wall.
31. The apparatus of claim 20 further including a melting chamber
which has a sidewall and in which the mold is disposed; and a
passage wall having an inner periphery defining a passage which
extends through the sidewall of the melting chamber and is adapted
for movement of the metal casting therethrough; and wherein the
molten bath is bounded by the inner periphery of the passage wall.
Description
BACKGROUND OF THE INVENTION
1. Technical Field
The invention relates generally to the continuous casting of
metals. More particularly, the invention relates to the protection
of reactionary metals from reacting with the atmosphere when molten
or at elevated temperatures. Specifically, the invention relates to
using a molten material such as liquid glass to form a barrier to
prevent the atmosphere from entering the melting chamber of a
continuous casting furnace and to coat a metal cast formed from
such metals to protect the metal cast from the atmosphere.
2. Background Information
Hearth melting processes, Electron Beam Cold Hearth Refining
(EBCHR) and Plasma Arc Cold Hearth Refining (PACHR), were
originally developed to improve the quality of titanium alloys used
for jet engine rotating components. Quality improvements in the
field are primarily related to the removal of detrimental particles
such as high density inclusions (HDI) and hard alpha particles.
Recent applications for both EBCHR and PACHR are more focused on
cost reduction considerations. Some ways to effect cost reduction
are increasing the flexible use of various forms of input
materials, creating a single-step melting process (conventional
melting of titanium, for instance, requires two or three melting
steps) and facilitating higher product yield.
Titanium and other metals are highly reactive and therefore must be
melted in a vacuum or in an inert atmosphere. In electron beam cold
hearth refining (EBCHR), a high vacuum is maintained in the furnace
melting and casting chambers in order to allow the electron beam
guns to operate. In plasma arc cold hearth refining (PACHR), the
plasma arc torches use an inert gas such as helium or argon
(typically helium) to produce plasma and therefore the atmosphere
in the furnace consists primarily of a partial or positive pressure
of the gas used by the plasma torches. In either case,
contamination of the furnace chamber with oxygen or nitrogen, which
react with molten titanium, may cause hard alpha defects in the
cast titanium.
In order to permit extraction of the cast from the furnace with
minimal interruption to the casting process and no contamination of
the melting chamber with oxygen and nitrogen or other gases,
current furnaces utilize a withdrawal chamber. During the casting
process the lengthening cast moves out of the bottom of the mold
through an isolation gate valve and into the withdrawal chamber.
When the desired or maximum cast length is reached it is completely
withdrawn out of the mold through the gate valve and into the
withdrawal chamber. Then, the gate valve is closed to isolate the
withdrawal chamber from the furnace melt chamber, the withdrawal
chamber is moved from under the furnace and the cast is
removed.
Although functional, such furnaces have several limitations. First,
the maximum cast length is limited to the length of the withdrawal
chamber. In addition, casting must be stopped during the process of
removing a cast from the furnace. Thus, such furnaces allow
continuous melting operations but do not allow continuous casting.
Furthermore, the top of the cast will normally contain shrinkage
cavities (pipe) that form when the cast cools. Controlled cooling
of the cast top, known as a "hot top", can reduce these cavities,
but the hot top is a time-consuming process which reduces
productivity. The top portion of the cast containing shrinkage or
pipe cavities is unusable material which thus leads to a yield
loss. Moreover, there is an additional yield loss due to the
dovetail at the bottom of the cast that attaches to the withdrawal
ram.
The present invention eliminates or substantially reduces these
problems with a sealing apparatus which permits continuous casting
of the titanium, superalloys, refractory metals, and other reactive
metals whereby the cast in the form of an ingot, bar, slab or the
like can move from the interior of a continuous casting furnace to
the exterior without allowing the introduction of air or other
external atmosphere into the furnace chamber.
BRIEF SUMMARY OF THE INVENTION
The present invention provides an apparatus comprising a continuous
casting mold adapted for producing a metal cast having an outer
periphery; a molten bath of a coating material disposed below the
mold and adapted for applying a coating of molten material to an
outer periphery of the metal cast to produce a coated metal cast;
and a cutting mechanism disposed below the molten bath and adapted
for cutting the coated metal cast while extending downwardly from
the mold to form cut segments of the coated metal cast.
The present invention also provides an apparatus comprising a
continuous casting mold adapted for producing a metal cast having
an outer periphery; a molten bath of a coating material disposed
below the mold and adapted for applying a coating of molten
material to the outer periphery of the metal cast to produce a
coated metal cast; a metal cast pathway extending from adjacent the
mold to adjacent the molten bath and adapted for movement of the
metal cast therein from the mold to the molten bath; and a first
heat source disposed below the mold, above the molten bath and
adjacent the pathway whereby the first heat source is adapted for
heating the metal cast as it moves along the pathway.
The present invention further provides an apparatus comprising a
continuous casting mold adapted for producing a metal cast having
an outer periphery; a molten bath of a coating material disposed
below the mold and adapted for applying a coating of molten
material to the outer periphery of the metal cast to produce a
coated metal cast; and a source of particulate material and a
dispenser for dispensing the particulate material to a location
adjacent the molten bath.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
FIG. 1 is a sectional view of the seal of the present invention in
use with a continuous casting furnace.
FIG. 2 is similar to FIG. 1 and shows an initial stage of forming
an ingot with molten material flowing from the melting/refining
hearth into the mold and being heated by heat sources over each of
the hearth and mold.
FIG. 3 is similar to FIG. 2 and shows a further stage of formation
of the ingot as the ingot is lowered on a lift and into the seal
area.
FIG. 4 is similar to FIG. 3 and shows a further stage of formation
of the ingot and formation of the glass coating on the ingot.
FIG. 5 is an enlarged view of the encircled portion of FIG. 4 and
shows particulate glass entering the liquid glass reservoir and the
formation of the glass coating.
FIG. 6 is a sectional view of the ingot after being removed from
the melting chamber of the furnace showing the glass coating on the
outer surface of the ingot.
FIG. 7 is a sectional view taken on line 7-7 of FIG. 6.
FIG. 8 is a diagrammatic elevational view of the continuous casting
furnace of the present invention showing the ingot drive mechanism,
the ingot cutting mechanism and the ingot handling mechanism with
the newly produced coated metal cast extending downwardly external
to the melting chamber and supported by the ingot drive mechanism
and ingot handling mechanism.
FIG. 9 is similar to FIG. 8 and shows a segment of the coated metal
cast having been cut by the cutting mechanism.
FIG. 10 is similar to FIG. 9 and shows the cut segment having been
lowered for convenient handling thereof.
Similar numbers refer to similar parts throughout the drawings.
DETAILED DESCRIPTION OF THE INVENTION
The seal of the present invention is indicated generally at 10 in
FIGS. 1-5 in use with a continuous casting furnace 12. Furnace 12
includes a chamber wall 14 which encloses a melting chamber 16
within which seal 10 is disposed. Within melting chamber 16,
furnace 12 further includes a melting/refining hearth 18 in fluid
communication with a mold 20 having a substantially cylindrical
sidewall 22 with a substantially cylindrical inner surface 24
defining a mold cavity 26 therewithin. Heat sources 28 and 30 are
disposed respectively above melting/refining hearth 18 and mold 20
for heating and melting reactionary metals such as titanium and
superalloys. Heat sources 28 and 30 are preferably plasma torches
although other suitable heat sources such as induction and
resistance heaters may be used.
Furnace 12 further includes a lift or withdrawal ram 32 for
lowering a metal cast 34 (FIGS. 2-4). Any suitable withdrawal
device may be used. Metal cast 34 may be in any suitable form, such
as a round ingot, rectangular slab or the like. Ram 32 includes an
elongated arm 36 with a mold support 38 in the form of a
substantially cylindrical plate seated atop of arm 36. Mold support
38 has a substantially cylindrical outer surface 40 which is
disposed closely adjacent inner surface 24 of mold 20 as ram 32
moves in a vertical direction. During operation, melting chamber 16
contains an atmosphere 42 which is non-reactive with reactive
metals such as titanium and superalloys which may be melted in
furnace 12. Inert gases may be used to form non-reactive atmosphere
42, particularly when using plasma torches, with which helium or
argon are often used, most typically the former. Outside of chamber
wall 14 is an atmosphere 44 which is reactive with the reactionary
metals when in a heated state.
Seal 10 is configured to prevent reactive atmosphere 44 from
entering melting chamber 16 during the continuous casting of
reactionary metals such as titanium and superalloys. Seal 10 is
also configured to protect the heated metal cast 34 when it enters
reactive atmosphere 44. Seal 10 includes a passage wall or port
wall 46 having a substantially cylindrical inner surface 47
defining passage 48 therewithin which has an entrance opening 50
and an exit opening 52. Port wall 46 includes an inwardly extending
annular flange 54 having an inner surface or circumference 56.
Inner surface 47 of port wall 46 adjacent entrance opening 50
defines an enlarged or wider section 58 of passage 48 while flange
54 creates a narrowed section 60 of passage 48. Below annular
flange 54, inner surface 47 of port wall 46 defines an enlarged
exit section 61 of passage 48.
As later explained, a reservoir 62 for a molten material such as
liquid glass is formed during operation of furnace 12 in enlarged
section 58 of passage 48. A source 64 of particulate glass or other
suitable meltable material such as fused salt or slags is in
communication with a feed mechanism 66 which is in communication
with reservoir 62. Seal 10 may also include a heat source 68 which
may include an induction coil, a resistance heater or other
suitable source of heat. In addition, insulating material 70 may be
placed around seal 10 to help maintain the seal temperature.
The operation of furnace 12 and seal 10 is now described with
reference to FIGS. 2-5. FIG. 2 shows heat source 28 being operated
to melt reactionary metal 72 within melting/refining hearth 18.
Molten metal 72 flows as indicated by Arrow A into mold cavity 26
of mold 20 and is initially kept in a molten state by operation of
heat source 30.
FIG. 3 shows ram 32 being withdrawn downwardly as indicated by
Arrow B as additional molten metal 72 flows from hearth 18 into
mold 20. An upper portion 73 of metal 72 is kept molten by heat
source 30 while lower portions 75 of metal 72 begins to cool to
form the initial portions of cast 34. Water-cooled wall 22 of mold
20 facilitates solidification of metal 72 to form cast 34 as ram 32
is withdrawn downwardly. At about the time that cast 34 enters
narrowed section 60 (FIG. 2) of passage 48, particulate glass 74 is
fed from source 64 via feed mechanism 66 into reservoir 62. While
cast 34 has cooled sufficiently to solidify in part, it is
typically sufficiently hot to melt particulate glass 74 to form
liquid glass 76 within reservoir 62 which is bounded by an outer
surface 79 of cast 34 and inner surface 47 of port wall 46. If
needed, heat source 68 may be operated to provide additional heat
through port wall 46 to help melt particulate glass 74 to ensure a
sufficient source of liquid glass 76 and/or help keep liquid glass
in a molten state. Liquid glass 76 fills the space within reservoir
62 and narrowed portion 60 to create a barrier which prevents
external reactive atmosphere 44 from entering melting chamber 16
and reacting with molten metal 72. Annular flange 54 bounds the
lower end of reservoir 62 and reduces the gap or clearance between
outer surface 79 of cast 34 and inner surface 47 of port wall 46.
The narrowing of passage 48 by flange 54 allows liquid glass 76 to
pool within reservoir 62 (FIG. 2). The pool of liquid glass 76 in
reservoir 62 extends around metal cast 34 in contact with outer
surface 79 thereof to form an annular pool which is substantially
cylindrical within passage 48. The pool of liquid glass 76 thus
forms a liquid seal. After formation of this seal, a bottom door
(not shown) which had been separating non-reactive atmosphere 42
from reactive atmosphere 44 may be opened to allow withdrawal of
cast 34 from chamber 16.
As cast 34 continues to move downwardly as indicated in FIGS. 4-5,
liquid glass 76 coats outer surface 79 of cast 34 as it passes
through reservoir 62 and narrowed section 60 of passage 48.
Narrowed section 60 reduces the thickness of or thins the layer of
liquid glass 76 adjacent outer surface 79 of cast 34 to control the
thickness of the layer of glass which exits passage 48 with cast
34. Liquid glass 76 then cools sufficiently to solidify as a solid
glass coating 78 on outer surface 79 of cast 34. Glass coating 78
in the liquid and solid states provides a protective barrier to
prevent reactive metal 72 forming cast 34 from reacting with
reactive atmosphere 44 while cast 34 is still heated to a
sufficient temperature to permit such a reaction. Coating 78 also
provides an oxidation barrier at lower temperatures.
FIG. 5 more clearly shows particulate glass 74 traveling through
feed mechanism 66 as indicated by Arrow C and into enlarged section
58 (Arrow D) of passage 48 into reservoir 62 where particulate 74
is melted to form liquid glass 76. FIG. 5 also shows the formation
of the liquid glass coating in narrowed section 60 of passage 48 as
cast 34 moves downwardly. FIG. 5 also shows an open space between
glass coating 78 and port wall 46 within enlarged exit section 61
of passage 48 as cast 34 with coating 78 moves through section
61.
Once cast 34 has exited furnace 12 to a sufficient degree, a
portion of cast 34 may be cut off to form an ingot 80 of any
desired length, as shown in FIG. 6. As seen in FIGS. 6 and 7, solid
glass coating 78 extends along the entire circumference of ingot
80.
Thus, seal 10 provides a mechanism for preventing the entry of
reactive atmosphere 44 into melting chamber 16 and also protects
cast 34 in the form of an ingot, bar, slab or the like from
reactive atmosphere 44 while cast 34 is still heated to a
temperature where it is still reactive with atmosphere 44. As
previously noted, inner surface 24 of mold 20 is substantially
cylindrical in order to produce a substantially cylindrical cast
34. Inner surface 47 of port wall 46 is likewise substantially
cylindrical in order to create sufficient space for reservoir 62
and space between cast 34 and inner surface 56 of flange 54 to
create the seal and also provide a coating of appropriate thickness
on cast 34 as it passes downwardly. Liquid glass 76 is nonetheless
able to create a seal with a wide variety of transverse
cross-sectional shapes other than cylindrical. The transverse
cross-sectional shapes of the inner surface of the mold and the
outer surface of the cast are preferably substantially the same as
the transverse cross-sectional shape of the inner surface of the
port wall, particularly the inner surface of the inwardly extending
annular flange in order that the space between the cast and the
flange is sufficiently small to allow liquid glass to form in the
reservoir and sufficiently enlarged to provide a glass coating
thick enough to prevent reaction between the hot cast and the
reactive atmosphere outside of the furnace. To form a metal cast
suitably sized to move through the passage, the transverse
cross-sectional shape of the inner surface of the mold is smaller
than that of the inner surface of the port wall.
Additional changes may be made to seal 10 and furnace 12 which are
still within the scope of the present invention. For example,
furnace 12 may consist of more than a melting chamber such that
material 72 is melted in one chamber and transferred to a separate
chamber wherein a continuous casting mold is disposed and from
which the passage to the external atmosphere is disposed. In
addition, passage 48 may be shortened to eliminate or substantially
eliminate enlarged exit section 61 thereof. Also, a reservoir for
containing the molten glass or other material may be formed
externally to passage 48 and be in fluid communication therewith
whereby molten material is allowed to flow into a passage similar
to passage 48 in order to create the seal to prevent external
atmosphere from entering the furnace and to coat the exterior
surface of the metal cast as it passes through the passage. In such
a case, a feed mechanism would be in communication with this
alternate reservoir to allow the solid material to enter the
reservoir to be melted therein. Thus, an alternate reservoir may be
provided as a melting location for the solid material. However,
reservoir 62 of seal 10 is simpler and makes it easier to melt the
material using the heat of the metal cast as it passes through the
passage.
The seal of the present invention provides increased productivity
because a length of the cast can be cut off outside the furnace
while the casting process continues uninterrupted. In addition,
yield is improved because the portion of each cast that is exposed
when cut does not contain shrinkage or pipe cavities and the bottom
of the cast does not have a dovetail. In addition, because the
furnace is free of a withdrawal chamber, the length of the cast is
not limited by such a chamber and thus the cast can have any length
that is feasible to produce. Further, by using an appropriate type
of glass, the glass coating on the cast may provide lubrication for
subsequent extrusion of the cast. Also the glass coating on the
cast may provide a barrier when subsequently heating the cast prior
to forging to prevent reaction of the cast with oxygen or other
atmosphere.
While the preferred embodiment of the seal of the present invention
has been described in use with glass particulate matter to form a
glass coating, other materials may be used to form the seal and
glass coating, such as fused salt or slags for instance.
The present apparatus and process is particularly useful for highly
reactive metals such as titanium which is very reactive with
atmosphere outside the melting chamber when the reactionary metal
is in a molten state. However, the process is suitable for any
class of metals, e.g. superalloys, wherein a barrier is needed to
keep the external atmosphere out of the melting chamber to prevent
exposure of the molten metal to the external atmosphere.
With reference to FIG. 8, casting furnace 12 is further described.
Furnace 12 is shown in an elevated position above a floor 81 of a
manufacturing facility or the like. Within interior chamber 16,
furnace 12 includes an additional heat source in the form of an
induction coil 82 which is disposed below mold 20 and above port
wall 46. Induction coil 82 circumscribes the pathway through which
metal cast 34 passes during its travel toward the passage within
passage wall 46. Thus, during operation, induction coil 82
circumscribes metal cast 34 and is disposed adjacent the outer
periphery of the metal cast for controlling the heat of metal cast
34 at a desired temperature for its insertion into the passage in
which the molten bath is disposed.
Also within interior chamber 16 is a cooling device in the form of
a water cooled tube 84 which is used for cooling conduit 66 of the
feed mechanism or dispenser of the particulate material in order to
prevent the particulate material from melting within conduit 66.
Tube 84 is substantially an annular ring which is spaced outwardly
from metal cast 34 and contacts conduit 66 in order to provide for
a heat transfer between tube 84 and conduit 66 to provide the
cooling described.
Furnace 12 further includes a temperature sensor in the form of an
optical pyrometer 86 for sensing the heat of the outer periphery of
metal cast 34 at a heat sensing location 88 disposed below
induction coil 82 and above port wall 46. Furnace 12 further
includes a second optical pyrometer 90 for sensing the temperature
at another heat sensing location 92 of port wall 46 whereby
pyrometer 90 is capable of determining the temperature of the
molten bath within reservoir 62.
External to and below the bottom wall of chamber wall 14, furnace
12 includes an ingot drive system or lift 94, a cutting mechanism
96 and a removal mechanism 98. Lift 94 is configured to lower,
raise or stop movement of metal cast 34 as desired. Lift 94
includes first and second lift rollers 100 and 102 which are
laterally spaced from one another and are rotatable in alternate
directions as indicated by Arrows A and B to provide the various
movements of metal cast 34. Rollers 100 and 102 are thus spaced
from one another approximately the same distance as the diameter of
the coated metal cast and contact coating 78 during operation.
Cutting mechanism 96 is disposed below rollers 100 and 102 and is
configured to cut metal cast 34 and coating 78. Cutting mechanism
96 is typically a cutting torch although other suitable cutting
mechanisms may be used. Removal mechanism 98 includes first and
second removal rollers 104 and 106 which are spaced laterally from
one another in a similar fashion as rollers 100 and 102 and
likewise engage coating 78 of the coated metal cast as it moves
therebetween. Rollers 104 and 106 are rotatable in alternate
directions as indicated at Arrows C and D.
Additional aspects of the operation of furnace 12 are described
with reference to FIGS. 8-10. Referring to FIG. 8, molten metal is
poured into mold 20 as previously described to produce metal cast
34. Cast 34 then moves downwardly along a pathway from mold 20
through the interior space defined by induction coil 82 and into
the passage defined by passage wall 46. Induction coils 82 and 68
and pyrometers 86 and 90 are part of a control system for providing
optimal conditions to produce the molten bath within reservoir 62
to provide the liquid seal and coating material which ultimately
forms protective barrier 78 on metal cast 34. More particularly,
pyrometer 86 senses the temperature at location 88 on the outer
periphery of metal cast 34 while pyrometer 90 senses the
temperature of passage wall 46 at location 92 in order to assess
the temperature of the molten bath within reservoir 62. This
information is used to control the power to induction coils 82 and
68 to provide the optimal conditions noted above. Thus, if the
temperature at location 88 is too low, induction coil 82 in powered
to heat metal cast 34 to bring the temperature at location 88 into
desired range. Likewise, if the temperature at location 88 is too
high, the power to induction coil 82 is reduced or turned off.
Preferably, the temperature at location 88 is maintained within a
given temperature range. Likewise, pyrometer 90 assesses the
temperature at location 92 to determine whether the molten bath is
at a desired temperature. Depending on the temperature at location
92, the power to induction coil 68 may be increased, reduced or
turned off altogether to maintain the temperature of the molten
bath within a desired temperature range. As the temperature of
metal cast 34 and the molten bath is being controlled, water
cooled-tube 84 is operated to provide cooling to conduit 66 in
order to allow particulate material from source 64 to reach the
passage within passage wall 46 in solid form to prevent clogging of
conduit 66 due to melting therein.
With continued reference to FIG. 8, the metal cast moves through
seal 10 in order to coat metal cast 34 to produce the coated metal
cast which moves downwardly into the external atmosphere and
between rollers 100 and 102, which engage and lower the coated
metal cast downwardly in a controlled manner. The coated metal cast
continues downwardly and is engaged by rollers 104 and 106.
Referring to FIG. 9, cutting mechanism 96 then cuts the coated
metal cast to form a cut segment in the form of coated ingot 80.
Thus, by the time the coated metal cast reaches the level of
cutting mechanism 96, it has cooled to a temperature at which the
metal is substantially non-reactive with the external atmosphere.
FIG. 9 shows ingot 80 in a cutting position in which ingot 80 has
been separated from the parent segment 108 of metal cast 34.
Rollers 104 and 106 then rotate as a unit from the receiving or
cutting position shown in FIG. 9 downwardly toward floor 81 as
indicated by Arrow E in FIG. 10 to a lowered unloading or discharge
position in which ingot 80 is substantially horizontal. Rollers 104
and 106 are then rotated as indicated at Arrows F and G to move
ingot 80 (Arrow H) to remove ingot 80 from furnace 12 so that
rollers 104 and 106 may return to the position shown in FIG. 9 for
receiving an additional ingot segment. Removal mechanism 98 thus
moves from the ingot receiving position of FIG. 9 to the ingot
unloading position of FIG. 10 and back to the ingot receiving
position of FIG. 9 so that the production of metal cast 34 and the
coating thereof via the molten bath is able to continue in a
non-stop manner.
Thus, furnace 12 provides a simple apparatus for continuously
casting and protecting metal casts which are reactionary with
external atmosphere when hot so that the rate of production is
substantially increased and the quality of the end product is
substantially improved.
In the foregoing description, certain terms have been used for
brevity, clearness, and understanding. No unnecessary limitations
are to be implied therefrom beyond the requirement of the prior art
because such terms are used for descriptive purposes and are
intended to be broadly construed.
Moreover, the description and illustration of the invention is an
example and the invention is not limited to the exact details shown
or described.
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